Ethylene Glycol → 2-(2-Bromo-5-fluorophenyl)-2-methyl-1,3-dioxolane

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Reaction Steps

Ethylene glycol (25.6 mL, 458 mmol) and p-toluenesulfonic acid (4.36 g, 22.9 g) were added to a solution of 1-(2-bromo-5-fluorophenyl)ethanone (10.5 g, 45.8 mmol) stirring in benzene (250 mL). The reaction mixture was equipped with a Dean Stark trap containing 4.0 angstrom molecular sieves and refluxed for 16 h. The reaction was transferred to a separatory funnel containing a 1:1 mixture of H2O and sat. NaHCO3 (aq) and extracted with EtOAc (3×100 mL). The combined organics were washed with H2O, brine, dried over Na2SO4 and concentrated. The resulting oil was purified by column chromatography to give 2-(2-bromo-5-fluorophenyl)-2-methyl-1,3-dioxolane (7.20 g) in 58% yield. 1H NMR (CDCl3, 300 MHz) δ2.60 (s, 3 H) 4.02-4.20 (m, 4H), 6.85-6.90 (m, 1H), 7.29-7.33 (m, 1H), 7.48-7.56 (m, 1H).

Provenance & Evidence